You could hedge your bets, at least for the first year. Getting the AMEX Platinum card gives unlimited US club access (as well as AA and DL access on a ticketed flight). Then for UA Club access, get the UA MileagePlus Club card with the waived annual fee for the first year, which gives full UA Club (and Star Alliance) access. This allows access to all three potential lounges you'd encounter until the dust settles.